Is it normal to want to be in a relationship with two people at the same time? And for those two people to not only know about one another, but are also dating eachother? For some reason the idea of being in a relationship like this is really appealing to me. I dunno why...

The girl was fully bi and basically the "anchor" point for both me and him, but as things go, me and him also did sexual stuff. We all lived together in a flat and basically worked like a "couple" with each another. It worked surprisingly well, for a time, so i guess it's understandable one would want to try and experience that for yourself. Do understand though that this requires a clear "definition" of roles to work out...basically one person as the "alpha"(the other girl), the partner(the guy), and the beta that submits to the others(Me).
If you try to set something like this up with all participants equal and with the same rights to one another, i see a recipe for disaster.
But for some reason many governments decided to make laws against polygamy even though it was very common throughout history.